A microcomputer-based instrument has been developed to study cellular energy transduction phenomena. Specially designed electrodes have been constructed and interfaced to the microcomputer to calculate membrane poetntial and protonmotive force. Derived parameters are recorded om realtime on a multipen plotter via D/A converters. The user can observe all parameters as he oerturbs alterations to the medium in which the respiring and energy transducing systems are suspended.